Chapter 29

Reflection and Refraction

• When waves interact with matter, they can be reflected, transmitted, or a combination of both.

• Waves that are transmitted can be refracted.

Reflection

• When a wave reaches a boundary between two media, usually some or all of the wave bounces back into the first medium.

• The part of the wave that comes back is the reflection.

Defining Normal?

• Normal: Perpendicular to the plane of a surface.

• The normal to the floor points straight up.

• The normal to the ceiling points straight down.

The Law of Reflection

Angle of Incidence = Angle of Reflection

Refraction • When a wave hits a boundary it changes its speed upon crossing the boundary between two media.

(Media is plural for medium)

• If that wave hits the boundary at any angle other than normal to the surface, it bends.

• This bending is called Refraction.

A Property of Matter

• Index of Refraction: A measure of how much slower light moves through a material.

• The higher the number, the slower light moves.

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μ =Speed of light in a vacuum

Speed of light in material

Toward Normalor Away From Normal

• When light moves from a lower Index of Refraction to a higher index of refraction, the wave bends towards the normal.

• When light moves from a higher Index of Refraction to a lower index of refraction, the wave bends away from the normal.

Effects of Refraction in Daily life

• Think for a moment• Write down what is going on in each picture.

Diffraction

• Bending of waves when they encounter an obstacle.